(1) Field of the Invention
This invention relates to novel chemical processes and compositions, particularly the utilization of novel copolymers of vinyl terminated propene polymers and activated unsaturated monomers, such as maleic anhydride, as intermediates for lubricant and fuel additives. Copolymers of the atactic polymers with activated unsaturated monomers such as maleic anhydride, and functionalization of the resulting intermediate copolymer compositions to provide effective lubricant and fuel additives are included in the invention. These compositions are useful as intermediates for dispersants used in lubricating oil compositions or as dispersants themselves. The dispersants of the present invention also advantageously impart fluidity modifying properties to lubricating oil compositions which are sufficient to allow elimination of some proportion of viscosity index improver from the lubricating oil compositions which contain these dispersants.
(2) Description of Related Art
Chemical additives for lubricating oils are used to control the physical and chemical properties of the oils. These additives are used to modify oil viscosity and viscosity index, to make the oils more resistant to oxidation, and to keep engines and other mechanical equipment clean and protected against corrosion and wear, and keep particulate matter dispersed to minimize or eliminate sludge and deposits.
Hydrocarbon-based chemical additives are designed for specific functions by choosing a hydrocarbon type and molecular weight range or molecular weight distribution to allow the additives to function in the fluid type of interest. For instance, high molecular weight polymers can be used to increase viscosity and viscosity index of mineral oils or synthetic oils. Polar head groups can be designed to be attached to low or high molecular weight hydrocarbon tails to achieve detergency, dispersancy, antiwear or anticorrosion performance.
Extensive use has been made of ethylene and butene or isobutylene oligomers in forming oil additives. High molecular weight ethylene-propylene olefin copolymers are commonly used to increase the viscosity index of lubricating oils. See, for example, U.S. Pat. No. 5,151,204 to Struglinski.
Free radical polymerization of vinylidene containing polymer with unsaturated acidic monomers is detailed in U.S. Pat. No. 5,112,507 to Harrison. Therein, at least about 20 percent of the total high molecular weight olefin comprises the alkylvinylidene isomer, the resulting copolymer product having alternating succinic and polyalkyl groups. Preferred high molecular weight olefins therein include polyisobutenes, especially polyisobutenes in which the alkylvinylidene isomer comprises at least 50 percent of the total olefin.
WO-A 95/07944 discloses the free radical polymerization of unsubstituted .alpha.-olefin based oligomer, an unsubstituted dicarboxylic acid or anhydride, and a monounsaturated compound to obtain a terpolymer for use as fuel and lubricant additive intermediates.
Alkenyl-substituted succinic anhydrides have been used as dispersants. Such alkenyl-substituted succinic anhydrides have been prepared by two different processes, a thermal process, referred to herein as "ene chemistry" (see, e.g., U.S. Pat. No. 3,361,673) and a chlorination process (see, e.g., U.S. Pat. No. 3,172,892). The polyisobutenyl succinic anhydride ("PIBSA") produced by the thermal process has been characterized to contain a double bond in the product. The chlorination process PIBSAs have been characterized as monomers containing either a double bond, a ring, other than a succinic anhydride ring and/or chlorine in the product. See J. Weill and B. Sillion, "Keaction of Chlorinated Polyisobutene with Maleic Anhydride:Mechanism Catalysis by Dichloromaleic Anhydride", Revue de l'Institut Francais du Petrole, Vol. 40, No. 1, pp. 77-89 (January-February, 1985). Such compositions include one-to-one monomeric adducts (see, e.g., U.S. Pat. Nos. 3,219,666; 3,381,022) as well as adducts having polyalkenyl-derived substituents adducted with at least 1.3 succinic groups per polyalkenyl-derived substituent (see, e.g., U.S. Pat. No. 4,234,435 to Meinhardt). PIBSA serves as a ubiquitous precursor to several commercial crankcase ashless dispersants, including succinimides, succinates, succinate esters, and triazoles.
U.S. Pat. No. 5,435,926 to Gutierrez et al. discloses ethylene-alpha-olefin copolymers including ethylene-propylene copolymers, but requires an average of at least about 30% of the polymer chains to contain terminal ethenylidene unsaturation. The disclosed copolymers are used to make alkenyl succinic anhydrides via ene chemistry. Only a minor amount of the polymer chains can contain terminal ethenyl, or vinyl, unsaturation. Also disclosed is the use of metallocene catalysts for production of ethylene-propylene copolymers containing high levels of terminal ethenylidene unsaturation.
Despite the vast amount of work conducted heretofore, a need exists for novel ashless dispersants that can enable use of smaller amounts of viscosity index improvers in formulating finished lubricants, giving a cost reduction. Because of the relatively high temperatures to which finished lubricating oils are exposed during actual service conditions, improved thermal stability is a desirable property in ashless dispersants. The advantages of having an ashless dispersant which contributes viscosity increase to the lubricant and thus reduces the amount of viscosity index improver needed in the finished oil is referred to, for example, in U.S. Pat. No. 4,234,435.